In general, most of the various kinds of conduits such as gas conduits, city water pipelines and sewers etc., as mentioned above, have a number of branched pipelines extending therefrom in regions close to the terminal ends thereof. For example, low pressure pipelines of gas conduits are buried in the ground under city roads to supply city gas through branched pipelines to neighboring houses or buildings. Many branched pipelines extend from a main pipeline at intervals of short distances. Further, the above-mentioned situation on the distribution of branched pipelines at terminal ends of gas main conduits is also applicable in the case of city water pipelines and conduits, for sewerage.
It is well known to apply a tubular lining material to the inner surfaces of such pipelines or conduits for the purpose of repairing or reinforcing them. Examples of such a lining method for pipelines are described, for example, in U.S. Pat. Nos. 4,368,091 and 4,334,943 wherein a tubular lining material made of a flexible material which has been applied to the inner surface thereof with a binder or adhesive is fixedly secured in an annular form at one end of a pipeline, and a fluid pressure is applied to the back of the annularly fixed portion to form a turning, point where the lining material is turned inside out. This allows the turning point to advance successively within the pipeline and reach the other end thereof by the action of the fluid pressure thereby inserting the evaginating lining material into the pipeline while the surface of the lining material which has been applied with the adhesive is being pressed against the inner surface of the pipeline. The adhesive is interposed in between their inner surfaces, and is solidified to effect bonding.
In the case where the inner surface of such a pipeline is applied with a lining material, the openings in the main pipeline from which the branched pipelines extend; that is the branched portions of the pipeline will also be lined so that the openings or passages leading to the branched pipelines will be blocked by the lining material. Accordingly, it is necessary to bore or port the lining material blocking the branched portions where the branched pipelines are connected to the main pipeline, after the lining process, to provide communication between the branched pipelines and the main pipeline.